I noticed on pysorg.com an interesting article about running gasifiers with a high Co2 level, basically it comes down to a better conversion ration of Biomass to char but it made me wonder about V Turbines plans to add a turbine pulse jet combination, there is scope I think for recirculating some of the pulse jet exhaust to the gasifier to raise the Co2 level as per this article and improve the overall conversion efficiency.

Some thing fun to add to the mix

I will see if I can find you the article link

Viv

"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them"Brock Clarke

I think one of vturbines early points was to use a pulse burner setup to bring the temperature of the char up over 4000F. (Not completely out of the question, as a good coal could exceed 3600F) Between approx. 4000 to 4500F steam disassociates and releases the H2 needed to recombine with the available Carbon left in the char. Without the additional H2, the yield may not increase much with the addition of CO and CO2.

With as much water is available it does make sense. The big problem I see with the theory is pushing the char from the 2000F range up to 4000F is a stretch.

Unfortunately this unit will probably not reach that temp as it would melt the lower flame tube and intake, grate etc.. Even a complete 304 stainless setup would give at 2650F. Probably would take a complete refractory unit to get there, but at least this thing is pulsing. I wonder how the NOx levels would be affected by the pulsing as compared to a typical unit?

It would be fun if this design could become strong enough to push a tiny turbine and produce copious fuel in the same setup. Oh well, this is my first gasifier build, guess should stick to the basics for now.

If where making liquid fuels from the wood gas it may be beneficial to run solar cells to power a efficient, robust electrolysis setup. Siphon off the O2 to the char to boost up to 4000F, and siphon the H2 with recirculated CO to boost the yield some.

Completed assembly and made a go of it last night. It became apparent in the first few minutes that something was wrong.

A substantial amount of steam was pouring out the exhaust, and the gas would not light. Brought on the bike pump to try to raise the temp., to no avail.

Pulled the plunger, and there it was again, that pesky condensation. Plunger looked as if it had been pulled out of a bucket of water. Inserted the plunger and continued. Only created gas 2 or 3 times, lasting less than a minute. (The unit didn't pulse at any time, even with height adjustment on the plunger.)

Thinking back, remembered that most of last week the mornings exhibited low lying fog.

The particular morning of the run, the fog didn't disperse until approx. 11:00 A.M. followed by humid, 80F+ afternoon. I reason the fuel must have picked up substantial amounts of moisture, that along with the high humidity of the ambient air was creating poor running conditions. What should have been the best run yet was mostly unproductive.

Mulling over the idea of a de-humidifier/drier for the fuel. Built on the unit somewhere. Would be nice to place it in a manner to both function as a partial hopper and drier.

This may sound counter intuitive but you may want to start up your gasifier with a big bag of ordinary barbecue charcoal for an hour or so before you try introducing your first fuel wood charge, it may just be that the initial wood charge is at too high a total humidity percentage to allow the gasifier to get to its running temperature, basically the water is stealing all your heat and never allowing it to get hot enough to make gas

Viv

"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them"Brock Clarke

Viv,
That sounds reasonable.
I think my starting temp is good. I start a initial wood fire outside the unit and transport the hot, dry coals over to the unit and fill just above intake pipe. Use the bike pump with attached blow pipe, down the flame tube to raise the entire coal bed up to between orange and yellow heat (reckon thats somewhere between 1400F to 2000F), then add the cold damp fuel and continue using the bike pump at the intake.

That being said, the specific heat of water is substantial and could quickly pull the coal bed down under the 1000F mark. Maybe adding a few inches of partial crushed charcoal between the hot coal bed and the damp fuel may give enough buffer heat to give a better start. Will try it on the next run and see how she does.

PyroJoe wrote:Completed assembly and made a go of it last night. It became apparent in the first few minutes that something was wrong.

A substantial amount of steam was pouring out the exhaust, and the gas would not light. Brought on the bike pump to try to raise the temp., to no avail.

Pulled the plunger, and there it was again, that pesky condensation. Plunger looked as if it had been pulled out of a bucket of water. Inserted the plunger and continued. Only created gas 2 or 3 times, lasting less than a minute. (The unit didn't pulse at any time, even with height adjustment on the plunger.)

Thinking back, remembered that most of last week the mornings exhibited low lying fog.

The particular morning of the run, the fog didn't disperse until approx. 11:00 A.M. followed by humid, 80F+ afternoon. I reason the fuel must have picked up substantial amounts of moisture, that along with the high humidity of the ambient air was creating poor running conditions. What should have been the best run yet was mostly unproductive.

Mulling over the idea of a de-humidifier/drier for the fuel. Built on the unit somewhere. Would be nice to place it in a manner to both function as a partial hopper and drier.

A wire basket atop the housing lid around the draft pipe would be a simpler solution for a dryer. Will try it this weekend.
A jam-jar fastened to a flame tube lid may be a reasonable condenser(pipe nipple passing through the lid open into the jar).

May need to try a larger diameter draft pipe, something read about in chimney design, mentioned a larger cross section area should result in increased flow.

Along with the height of the draft pipe, the average temperature difference between the flue gas, and the ambient air was also a driving factor. This passive approach with a draft pipe is probably more difficult than a typical mechanical driven gasifier.

Two days of rain on stick fuel is akin to someone whizzing in your fuel tank.

Disassembled the unit today, the ash has soaked up moisture, and is damp to the touch. I can squeeze a small hand full and it retains the shape of the inner hand. A full day of drying, and is still damp. While waiting, built a second lid and lower plate for a 1.66" diameter draft pipe. Not sure if it will be dry enough tomorrow.

If its any consolation its raining too here in the great white north thats a bit odd for this time of year in these parts as well, it does sound like your local conditions are far from optimal to get any good indicators from a test run, maybe worth taking a break till the weather clears up a bit?

Viv

"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them"Brock Clarke

Couple days of sunshine and the spirit is lifted. Dried the ash. After doing some tests by heating a pipe buried in wet ash there is little concern with the ash picking up moisture. A heated pipe will slowly cook of the moisture to about .5" depth. The remaining moisture will cook off and disperse in an absurd slow rate (unless stirred for hours and hours and hours and hours.....), I guess do to the insulating/sealing effect of the ash.

One future improvement would be to use only 2" of ash above the lower chamber to seal the unit, then above the ash, use lava rock to fill the remaining volume. Possibly aluminum foil between to keep the rock clean.